JPS58198962A - Scanner for light beam - Google Patents

Abstract

PURPOSE:To deal with a change in the transfer speed of video data without varying the rotating speed of a rotating polygon mirror and to scan a light beam excellently, by performing speed conversion of video data with a slow transfer speed to video data with a reference transfer speed, and modulating the light beam according to the video data. CONSTITUTION:Input video data is stored in a memory 62 within the range of the conversion synchronizing signal of a synchronizing signal conversion part 44 at the timing of output pulses of a pulse frequency division part 42. Then, the contents of the memory 62 are outputted and a photosensitive drum 18 is irradiated with a laser beam to form a latent image. The video data is outputted from the memory 62 within the range of the synchronizing signal of a synchronizing signal frequency division part 41 at the timing of output pulses of a synchronization part 84. Namely, the output operation is carried out nearly twice as fast as the storage to the memory 62. The laser beam is modulated on the basis of the video data to form a latent image as the 1st line.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a light beam scanning device, in particular, to scan a laser beam by rotating an optical device such as a rotating polygon mirror or a rotating prism, and to transmit an image signal. The present invention relates to a light beam scanning device with variable speed.

Light beam scanning devices are used in facsimile transmission/reading and reception/recording devices as well as laser printers and the like. Among these, an example of a scanning device for a light beam, particularly a laser beam, used in a laser printer is shown in FIG. In this figure, a laser beam emitted from a light source 11 for laser generation is modulated by a light modulation unit 13 made of an acousto-optic element via a shutter 12, and is modulated by a rotating polygon mirror 15 that is rotationally driven by a drive unit 16. (hereinafter, this scanning will be referred to as "main scanning"). This main-scanned laser beam reaches a sensor 20 consisting of a light-receiving element and a photosensitive drum 18 on which an image is recorded as a latent image. Scanning is performed in a direction perpendicular to the main scanning (hereinafter, this scanning will be referred to as "sub-scanning").

On the other hand, the detection output of the sensor 20 is transmitted to the synchronization signal generator 21.
Here, a necessary synchronization signal is formed and input to the control section 22. Appropriate video data sent from the outside in synchronization with the synchronization signal is input to the terminal TM of the control section 22, and the high frequency signal output from the oscillator 23 in the modulator 24 is input to the terminal TM of the control section 22. Modulated based on data. Furthermore, this modulation signal is amplified by an amplifier 25 and then input to the optical modulation section 13, where the laser beam is modulated.

Further, the ill m1 section 22 outputs an appropriate control signal to the drive section 19 of the photosensitive drum 18, thereby controlling the sub-scanning.

In a light beam scanning device having such a configuration, there is a close relationship between the video data transfer speed and the main scanning and sub-scanning speeds, and the resolution of the image is affected by the degree of these factors.

Therefore, when the main scanning speed and sub-scanning speed are determined for a certain transfer rate (hereinafter referred to as RL semi-transfer rate), when video data is sent at a transfer rate lower than the reference transfer rate, , the main scanning and sub-scanning speeds must also be set to low values. As mentioned above, the main scanning is performed by the rotating polygon mirror 15, and the sub-scanning is performed by the photosensitive drum 18. Of these, the sub-scanning can be performed relatively easily by using a pulse motor or the like as the drive unit 19. Speed control is possible.

However, it is extremely difficult to continuously vary the rotation speed of the rotating polygon mirror 15 over a wide range and to operate it stably at any speed. For this reason, in the past, the low speed motor, drive circuit, and power supply were designed separately and replaced with those for the standard transfer speed to accommodate changes in the video data transfer speed. Therefore, such conventional means cannot cope with various changes in the transfer speed of video data.

This invention has been made in view of the above-mentioned circumstances, and provides an optical beam that can scan a light beam in a manner that satisfies changes in video data transfer speed without changing the rotation speed of a rotating polygon mirror. Its purpose is to provide a beam scanning device that converts the video data transfer rate to a predetermined reference transfer rate, and drives a rotating polygon mirror to rotate at a rotation speed corresponding to the reference transfer rate. This objective is achieved by outputting video data in a synchronized manner and performing light beam modulation.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The light beam scanning @pupil according to the present invention will be described in detail below according to embodiments shown in the accompanying drawings.

First, the outline will be explained according to FIGS. 2(A) to 2(C).

2 (A) to (C), in (A) - the image is R
In the figure, the - line indicates a latent image composed of 611 dots D1 to D6. In reality, the number of lines and the number of dots are very large, but for the sake of explanation, it is assumed as shown in FIG. 2 (A>. First, the photosensitive drum 18 shown in FIG. Ll is set.Next, the rotating polygon #R15
Dots D1 to D6 are formed on the photosensitive drum 18 by the rotation of the dots D1 to D6.
A laser beam corresponding to is incident. The above operations are repeated to form the image shown in FIG. 6 of hours
times, and this increases the scanning time of dots D1 to D6 by T
It corresponds to

Now, assuming that the sub-scanning speed, that is, the rotational speed of the photosensitive drum 18 is reduced to 1/2, and the video data transfer speed is the same and remains unchanged, the dot D1 as shown in FIG. 2 (8) to D6 overlap in the sub-scanning direction.

In order to prevent this, the laser beam irradiation may be omitted every other row as shown in FIG. 2(C). That is, the laser beam is irradiated only once out of two main scans performed within a time approximately twice the scanning time ΔT. In other words, the plurality of reflective surfaces (
6 planes in Fig. 1), one plane corresponds to one line of main scanning according to its rotation, but in Fig. 2 (C)
As a result, two surfaces correspond to one row of main scanning.

Based on the following ten assumptions, the video data transfer speed is 1/
2, the transfer time of the video data constituting the - row is 2ΔT, which is twice the above-mentioned ΔT. That is, video data regarding dots D1 to D6 is transferred at a time interval of 2ΔT. If this video data is once stored in memory and then output at the same transfer speed as shown in FIG. 2(A) to perform main scanning with the laser beam,
First, for the first row of dots D1 to D6, ms can be formed on the photosensitive drum 18 without changing the rotational speed of the rotating polygon mirror 15 in any way.

Next, if we set the sub-scanning speed to 1/2 and not only keep the rotational speed of the rotating polygon 115 as it is but also do not irradiate the laser beam, the second line L2 will be as shown in FIG. 2(C). Become. The same applies to the third line L3 and subsequent lines. That is,
When the video data transfer speed becomes 1/2, -scanning speed ° is reduced to 1/2, the video data transfer speed is output at the original speed, and every other main scanning line is output. If laser beam irradiation is performed, changes in the transfer speed can be accommodated without changing the rotation speed of the rotating polygon mirror 15. The same applies when the transfer rate becomes 1/n.

Next, FIGS. 3 and 4 show an example of a configuration for scanning a light beam according to the present invention. FIG. 3 schematically shows the appearance of the entire structure, FIG. 4 shows the electrical structure, and FIG. 5 shows an example of operation.

Of these, in FIG. 3, the light emitted from the laser light source 11 is modulated by image information by the light modulator 13 via the shutter 12, and then passes through the lens system 14.17 to the surface of the photoreceptor. It reaches the top of the photosensitive drum 18, which is currently being used. At this time, light is caused to scan the photosensitive drum 18 in the range indicated by the arrow F1 in the figure by the rotating polygon mirror 15 driven by the drive section 16. Photosensitive drum 1
8 is rotated in a predetermined manner by a drive unit 19, so that image information is recorded on the photosensitive jζ ram 18 as a latent image. Further, the outer periphery of the photosensitive drum 18 is provided with devices (not shown) for development, transfer, fixing, cleaning, charging, etc., so that printing can be performed on a predetermined sheet of paper.

Furthermore, within the scanning range indicated by the arrow F1 mentioned above, a sensor 20 consisting of a light receiving element is provided in the stomach at the starting point of scanning, and is connected to a control device 30 which will be described later. The control device 130 has a circuit configuration as shown in FIG. 4, and has a function of controlling scanning of a laser beam.

Next, in FIG. 4, the optical modulator 13 includes an oscillator 3
A high-frequency carrier wave outputted by the laser light source 11 is modulated by a modulator 32 using video data, and is further amplified and inputted by an amplifier 33.
The laser beam emitted by the is modulated.

The rotating polygon mirror 15 has reflective surfaces S1 to S6, and a controller 26 is connected to the drive unit 16 so that the rotating polygon mirror 15 is rotated at a predetermined rotational speed in a constant cycle with other components described below. It is controlled so that it rotates.

Next, the scan control circuit includes a timing section 40 that generates a timing signal necessary for control, a speed conversion section 60 that converts and outputs the transfer speed of video data transferred from the terminal TM, and the timing section It has a synchronization control section 80 that synchronizes the timing of the signal generated by 40 and the timing of main scanning and sub-scanning. Of these, the synchronization control unit 8° first generates a constant pulse (see FIG. 5 (b)) to make the laser beam incident on the sensor 20 in order to determine the reference timing for main scanning. S.O.
It has an S gate generation section 81.

That is, the output pulse of the SOS gate generator 81 is input to the modulator 32 via the terminal 82 and further reaches the optical modulator 13. As a result, the laser beam enters the sensor 20, and the sensor 20 outputs a pulse for main scanning control (hereinafter referred to as the rsos signal) (see Fig. 5 (c)), and this SO8 signal becomes the main scanning reference. Become. This SO8 signal is inputted to the SOS gate generation section 81 together with the output pulse of the oscillator 83 and becomes the basis for the timing of the next pulse output, and is inputted to the synchronization section 84 and the synchronization signal generation section 85, respectively.

Among these, the synchronizing section 84 has a function of synchronizing the output pulse of the oscillator 83 with the SO8 signal and outputting it (see FIG. It corresponds to 11 nits. Further, the synchronization signal generating section 85 generates a synchronization signal for determining an effective scanning range in which latent image formation is performed in the main scanning of the laser beam on the photosensitive drum 18 based on the SO8 signal and the output pulse of the synchronization section 84. It has an output function (see Figure 5). Therefore, in normal beam scanning at the standard transfer rate, main scanning of the laser beam may be performed at the timing of the output pulse of the synchronizing section 84 within the period of the synchronizing signal output from the synchronizing signal generating section 85. In the example shown in FIG. 5, for ease of understanding, one main scanning line is made up of 13 dots.

Next, the timing section 40 receives a synchronization signal, a branch section 41,
By operating the selection unit 43, the video data transfer rate is specified as a fraction of the reference transfer rate (hereinafter, this specified value will be referred to as r 1/n).
Based on this, the four arithmetic signal branching section 41
and the pulse branching section 42 are operated. First, the synchronization signal division section 41 receives the output synchronization signal of the synchronization signal generation section, and has a function of dividing the frequency of the synchronization signal into 1/n according to the specified value 1/n of the selection section 43 and outputting the result. (See Figure 5 (g)).

Next, the output pulse of the oscillator 83 is inputted to the pulse division section 42, which also has the function of dividing the frequency into the designated ring 1/n of the selection section and outputting it (see Fig. 5 (H)). reference).

Further, the timing section 44 is provided with a synchronization signal conversion section 44, into which the outputs of the synchronization signal division section 41 and the pulse division section 42 are respectively input, and pulse division is performed from the rising edge of the output of the synchronization signal division section 41. It has a function of counting the output pulses of the peripheral part 42 and outputting a synchronizing signal until the number of dots equals one line of main scanning (see FIG. 5).

Furthermore, the speed converter 61 includes a denial line buffer memory (hereinafter simply referred to as "memory") 62, 63 and a memory controller 61, and the input/output of the memory 62, 63 is controlled by the memory controller 61. It is now possible to do so. Video data input to the memory 62.63 is performed from terminal TM via terminal 64, and video data output from memory 62.63 is provided to terminal 65.63.
The signal is input to the modulator 32 via 82. On the other hand, the outputs of the pulse frequency divider 42 and the synchronization signal converter 44 are first input to the memory controller 61, and video data for one line of main scanning is alternately stored in the memories 62 and 63 according to the timing of these signals. The input is now memorized. The terminal 64 is for selecting the input direction of video data. Further, the outputs of the synchronizing section 84 and the synchronizing signal frequency dividing section 41 are input to the memory controller 61, and the contents of the memories 62 and 63 are read out and output in accordance with the timing of these signals. Terminal 65 is for selecting and connecting memory 62 or 63 for outputting video data.

Note that the selection section 43 is connected to the drive section 19 of the photosensitive drum 18, and selects a rotational speed of 11 [t] based on the specified value 1/n.
That is, the photosensitive drum 18 is moved so that the sub-scanning speed is 110.
is driven and controlled. Furthermore, this drive section 19 and the drive section 16 of the rotating polygon mirror 15 are connected to a controller 26, and drive control is performed in a synchronized manner based on a signal from a synchronization control section 80. This is similar to the conventional technology.

Next, the overall operation of the above embodiment will be explained with reference to FIG. 6 in addition to FIGS. 2 to 5 described above. Furthermore, the 6th
This figure corresponds to FIG. 2(C) and shows the state of the latent image formed on the photosensitive drum 18 according to the time chart shown in FIG. Further, FIG. 5 shows an example where n=2 and the video data transfer speed is halved, and one main scanning line is composed of 13 dots.

First, according to an operator's instructions or a control signal included in video data, the laser light source 11 and the rotating polygon 115 are
, the photosensitive drum 1B is driven, and the SOS gate generating section 81
outputs a pulse at time T1 (see FIG. 5(b)). This is input to the modulator 32, and the high frequency carrier wave output from the oscillator 31 is modulated. This modulated carrier wave is input to the optical modulator 13 via the amplifier 33, and the laser beam is modulated and the rotating polygon 1115 sends the sensor 20 to the optical modulator 13.
incident on . The reflective surface at this time is 85 (see FIG. 5).

The synchronization unit 84 to which the SO8 signal (see FIG. 5 (c)) which is the output of the sensor 20 is inputted, outputs the output pulse of the oscillator 83 (see FIG. 5 (d)) in synchronization with the SO8 signal. (See Figure 5 (e)). Upon receiving this output, the synchronization signal generator 85 outputs a synchronization signal (see Fig. 5).
reference). The range of this synchronization signal includes 13 output pulses of the synchronization section 84, which corresponds to the number of dots in - rows. Furthermore, this synchronization signal is input to the synchronization signal division section 41 and divided into 1/2 (see FIG. 5 (G)), while the output of the oscillator 83 is input to the pulse division section 42 and similarly divided into 1/2. (See Figure 5 (H)). Further, these frequency-divided signals are input to the synchronization signal converter 44,
Another synchronization signal is issued (see FIG. 5(S)). This synchronizing signal (hereinafter referred to as the "variable IIk four-phase signal") includes 13 output pulses from the pulse branching section 41 within its range, and corresponds to the number of dots in - rows. Further, the length of the converted synchronization signal is approximately twice that of the synchronization signal that is the output of the synchronization signal generation section 85 or the synchronization signal frequency division section 41. That is, the synchronization signal shown in FIG. 13 output pulses from the pulse division section 42, which is 1/2 of the 84 output pulses, are included.'1...
.

The length of the signal is approximately doubled.

Next, the input h video data is as shown in Figure 5 (N),
- The transfer time of data for a row is twice the period of the SO8 signal. Of these, the video data corresponding to the first row is input to the memory 62 as shown in FIG. That is, the signals are input and stored in the memory 62 according to the timing of the output pulse of the pulse frequency dividing section 42 within the range of the converted synchronizing signal of the synchronizing signal converting section 44. This operation is performed from time T2 to time T3, and during this time the rotating polygon mirror 15
rotates by two main scanning lines, and at time T4 the reflection l1IS1
is 1 at the point where the laser beam is incident. The photosensitive drum 1B also rotates by two rows, and the next row is set at time T4. This line becomes the first line.

From time T4 to time T5, the contents of the memory 62 are output,
A laser beam is irradiated onto the photosensitive drum 18 to form a latent image. Video data output from the memory 62 is performed within the range of the synchronization signal from the synchronization signal division section 41 and in accordance with the timing of the output pulse from the synchronization section 84. That is,
The output is performed at approximately twice the speed of the time required to store it in the memory 62 (see Figure 5). The laser beam is modulated based on this video data, and the latency in the first row is An image will be formed, that is, the first line Ll in FIG.
The dot OA is irradiated with a laser beam based on the timing of the pulse PA in FIG. 5(E), and the dot DB is irradiated with a laser beam based on the timing of the pulse PB to form a latent image. The same applies to dots DC to DM. This main scanning is performed by the reflecting surface S1 of the rotating polygon mirror 15 (see FIG. 5 (see 1!)).

On the other hand, from time T4 to T6, the data corresponding to the second row at the back of the video data changes to 1(
The data is input and stored in the memory 63.

Historically, at time T5, the photosensitive drum 18 is set to the second row, and the rotating polygon mirror 15 starts main scanning with the reflecting surface S2, but since no video data is output, the laser beam is not irradiated, and the latent image is is not formed (Fig. 5 (Y))
, (evening), (see)) above times ■5 to ■6 are the 6th
This corresponds to the second line 12 in the figure.

Next, from time T6 to T7, the video data corresponding to the second row is output from the memory 63, and the latent image of the third row L3 in FIG. 6 is formed. The third row of data is in memory 6
2 is input and stored. Further, from time T7 to time T8, the operation corresponding to the fourth line L4 shown in FIG. 6 is performed.

The same holds true after time T8.

As is clear from the above operation, when the transfer rate of input video data is 1/2 of the standard transfer rate, it is stored in the memory 62 or 63 at 1/2 the rate,
Next, by outputting video data from the memory 62 or 63 at the reference transfer rate and modulating the laser beam, main scanning can be performed satisfactorily without changing the rotational speed of the rotating polygon mirror 15. . That is, the laser beam is incident on every other reflecting surface S1 to S6 of the rotating polygon mirror 115 and main scanning is performed, resulting in a main scanning speed of 1/2, but the rotation of the rotating polygon mirror 15 is The speed remains unchanged and remains constant. Note that the rotational speed of the photosensitive drum 18, which is the sub-scanning speed, is 1/2, so the line spacing is 1/2.
Since the laser beam is made to be incident on the photosensitive drum 18 every other row in correspondence with the laser beam being incident on every other back of the reflective surfaces S1 to S6, a latent image can be formed well.

In the above embodiment, the specified value of the selection section 43 is 1.
/2 is shown, but the present invention is not limited to this in any way, and the specified value may be arbitrarily determined. However, if the video data transfer rate is higher than the standard transfer rate, it cannot be handled, so the standard transfer rate, that is, the transfer rate when the specified value 1/n = 1, is the transfer rate that is possible in the system. It is preferable to set the rotational speed of the rotating polygon 115 so as to have a high speed. In addition, in the above embodiment, a case where one line is represented by 13 dots is shown, but this is for the sake of explanation, and in reality, for example, for example, one line in column B of the Japanese Industrial Standards, number 4, has a resolution of 12 dO1/j1.
If it is 1I, it will consist of 3640 dots.

Furthermore, although the above embodiments show a case where the light beam scanning device according to the present invention is applied to a laser printer that prints images based on video data transferred from an external source, conversely, when video data is transferred from an external source, The present invention can also be applied to cases where . For example, this is applied to a facsimile original transmitting device. If it is necessary to reduce the video data transfer rate to 1/n due to the design specifications of the other party's terminal device or the transmission capacity of the communication line used, the document feeding speed (corresponding to the rotational speed of the photosensitive drum 18) ) is set to 1/n, and information is read and stored in the memory once every n times of main scanning by the rotating polygon mirror 15 or the like. This operation is performed at the standard transfer rate. Next, this stored content is read out and output at a transfer rate of 1/n of the reference transfer rate. In this way, there is no need to change the rotation speed of the rotating polygon mirror 15, and the memory capacity can be reduced to two lines. Other circuit configurations may be used as long as they have the functionality.

As explained above, according to the light beam scanning device according to the present invention, video data with a slow transfer rate is converted into video data with a standard transfer rate, and the light beam is modulated according to this video data. Therefore, it is possible to keep the rotational speed of the rotating polygon mirror constant at a value corresponding to the reference transfer speed, to be able to respond to changes in the video data transfer speed without making any changes, and to perform light beam scanning successfully. It has the excellent effect of being able to

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an example of a laser beam scanning device, Figs. 2 (A) to (C) are explanatory diagrams showing an example of a latent image on a photosensitive drum, and Fig. 3 is a diagram according to the present invention. FIG. 4 is a block diagram showing the electrical configuration of the device shown in FIG. 3. FIG. FIG. 6 is an explanatory diagram showing the m-image formed on the photosensitive drum by the operation shown in FIG. 5. 15... Rotating polygon mirror, 18... Photosensitive drum having a scanned surface, 40... Timing section, 60... Speed conversion section, 80... Synchronization IJIII section.

Claims (1)

[Claims] A rotating polygon mirror and a scanning surface that are driven in accordance with a predetermined reference transfer rate of video data, and a synchronization control unit that outputs a signal necessary for light beam irradiation using video data in accordance with the speed. In the light beam scanning device having the above, when the transfer speed of video data is changed from the reference transfer speed, the video data is inputted at the changed transfer speed and synchronized with the driving of the rotating polygon mirror. a speed conversion unit that outputs video data at a reference transfer rate; and a timing unit that outputs a timing signal for video data input/output operations of the speed conversion unit based on an output signal of the synchronization control unit and transfer rate change data. A light beam scanning device comprising: